Fix deep property access in TypeScript.

[bm-w]

A couple of stanzas were only matching member_expression syntax nodes that had as their object: field either another member_expression or an identifier syntax node. E.g.:

[
  (nested_identifier object:(_)@mod)
  (member_expression object:[(member_expression) (identifier)]@mod)
]@nested {
  node @nested.expr_def
  node @nested.type_def

  edge @nested.expr_def -> @mod.expr_def
  edge @nested.type_def -> @mod.type_def
}

However, if that object was itself a member_expression the stanzas would create edges to its expr_[dr]ef graph nodes indiscriminately, regardless of whether it would itself be matched and thus those nodes created. In a “deep” property access involving two nested member_expressions and a third non-matching inner syntax node, e.g. a parenthesized_expression, these stanzas would cause errors, e.g.:

0: Error executing statement edge @nested.expr_def -> @mod.expr_def at (2377, 3)
     src/stack-graphs.tsg:2377:3:
     2377 |   edge @nested.expr_def -> @mod.expr_def
          |   ^
     in stanza
     src/stack-graphs.tsg:2371:1:
     2371 | [
          | ^
     matching (member_expression) node
     test/expressions/access-properties.ts:15:5:
     15 |     (x).y.z;
        |     ^
1: Evaluating edge sink
2: Undefined scoped variable [syntax node member_expression (15, 5)].expr_def

The fragment of the parsed Tree-sitter tree for such a deep property access is:

(member_expression ; Matching fine, `expr_[dr]ef` graph nodes created, but edge creation would fail
  object: (member_expression; Not matching, so `expr_[dr]ef` graph nodes not created
    object: (parenthesized_expression …)
    …)
  …)

Separating graph nodes and edges creation fixes the issue. Copious testing (on our TS test suite and on all of microsoft/vscode) reveals no negative side effects.